They come from every corner of America's galaxy – moms and dads, skywalkers and hobbits, students and pensioners, vampires and vigilantes, all on the same mission: escape.

It doesn't matter whether they dress up, whether it's their first or 30th time, whether they borrow or beg to get tickets, because once here they all escape, for a few days, from quotidian drudge.

Mae Lynn Yang, 23, resplendent in a white tunic and red wig with a plastic hatchet in her hand, was no longer Mae Lynn Yang who earns the near minimum wage in a New York cinema, but Codex, a warrior priestess of the Knights of Good from the web series The Guild. "This is a break," she said. From what? "From everything."

Welcome to Comic-Con, the pop culture expo that every year turns San Diego's cavernous convention centre into a portal to fantasy worlds usually lived out in imaginations but here exhibited and celebrated in the open.

"I made the costume 25 years ago but the horns are new," said Elizabeth Deboer, a retired teacher with black and blue satin robes, a demonic black hat and a stuffed raven attached to her wheelchair. This week she is Maleficent, the "mistress of all evil" from the Sleeping Beauty fable. "Later I'll be changing into the Red Queen."

Most of the 130,000 visitors– the lucky ones out of more than a million who applied for tickets – do not dress up. But they all conspire to make what is ostensibly a trade fair for graphic novels, films, TV shows and video games into an exercise in self-enchantment, a return to the idea of an America where you can be anything you want. And if it doesn't work out, well, maybe a superhero will step in.

"As an American art form comics came out of the Depression," said Rob Salkowitz, author of Comic-Con and the Business of Pop Culture. "It was escapism and wish fulfilment then and is the same today, especially with the economy in difficulty."

The $40 (£26) daily ticket price was affordable for most, he said. "What you're seeing here is the patient, not the privileged. Being super-rich doesn't buy you a better experience."

Larry Thomas, better known as the Soup Nazi from Seinfeld, noted it even among fans queuing at his stall for $20 autographed ladles. "A lot of people are struggling. Jobs are really hard to find. But they can still find a few bucks to come here."

From a neighbouring stall the actor Richard Anderson, or Oscar from the Six Million Dollar Man 1970s TV series, sensed nostalgia amid the sneak previews and merchandise for new blockbusters. "People don't feel too good but they remember better days."

The crush and queues – fans of Twilight camped outside for three days to see a panel discussion with cast and crew – dented exuberance not a whit. Klingons, zombies, Batmen, stormtroopers, wizards, gladiators, all chasing their own agendas but all sharing a camaraderie and unspoken pact to not break the spell.

"This trip was a gift from my dad. It's the only thing we had to look forward to this year," said Emily Furlong, 24, who, like her friend, Troy Stiegerwald, 28, is a student deep in debt. The same blissful enthusiasm pervaded all the fantasy worlds, no matter if they were filled with trolls, assassins, Nazi zombies, or, in the case of the new Lara Croft Tomb Raider video game, would-be rapists. The bad guys ended up splattered.

The British contingent, dispersed over different exhibitions and booths, slipped seamlessly into the narrative: James Bond gadgets, 2000 AD comic's Judge Dredd, the BBC with Dr Who – pitching heroes who always prevail.

Hard-headed business deals, marketing and networking occurred in the background. Marvel, on a roll from The Avengers film (Avengers Assemble in the UK), hoped to keep its momentum by building hype for Iron Man 3. DC Comics, struggling after several duds, hoped to restore lustre with The Dark Knight Rises and the Superman reboot.

Arnold Schwarzenegger and Sylvester Stallone turned up to promote The Expendables 2 at a packed panel they shared with Dolph Lundgren, ex-NFL player Terry Crews and martial arts champion Randy Couture.

"If there was a fight between the five of you right now, who would win?" asked one fan, shaming all the journalists with their infinitely more boring questions. "Whoever has the best lawyer," replied a grinning Stallone.

In fact pretty much everyone who attends Comic-Con wins, said Dennis Hanon, accountant by profession, Klingon fleet commander K'Han Den by vocation. In a theatrical play with other Klingons last year he was shot, supposedly fatally. "But here I am again."

The fleets of buses that ferry attenders back to their hotels after a day tramping around stalls and inhabiting other worlds are quiet. Passengers are tired and content, the private reels in their imaginations still playing.